This is possible because the scatterers increased the effective aperture of the array.

Because the length of this antenna is significantly smaller than a wavelength the effective aperture is approximately:

A similar nine segmented device would require 45 mW to support the same link with the same overall effective aperture.

A real small antenna will have a smaller effective aperture because of its lower gain.

Even for a receiving antenna, it is more usual to state the gain than to specify the effective aperture.

The effective aperture is however of interest for comparison with the actual physical size of the antenna.

The smaller the f/number, the larger the effective aperture.

The present system of f/numbers to give the effective aperture of a lens was standardized by an international convention.

It has a 0.22 light-years effective aperture and 427 light-years focal length.

In this method, multiple spatially modulated illumination patterns are used to double the effective numerical aperture.